Overview
DESCRIPTION Dipyridamole is a platelet inhibitor chemically described as 2,2',2'',2'''-[(4,8-Dipiperidinopyrimido[5,4- d ]pyrimidine-2,6-diyl)dinitrilo]-tetraethanol. It has the following structural formula: C 24 H 40 N 8 O 4 Mol. Wt. 504.63 Dipyridamole, USP is intensely yellow crystalline powder or needles.
Mechanism of Action
CLINICAL PHARMACOLOGY It is believed that platelet reactivity and interaction with prosthetic cardiac valve surfaces, resulting in abnormally shortened platelet survival time, is a significant factor in thromboembolic complications occurring in connection with prosthetic heart valve replacement. Dipyridamole tablets have been found to lengthen abnormally shortened platelet survival time in a dose-dependent manner. In three randomized controlled clinical trials involving 854 patients who had undergone surgical placement of a prosthetic heart valve, dipyridamole tablets, in combination with warfarin, decreased the incidence of postoperative thromboembolic events by 62 to 91% compared to warfarin treatment alone.
Indications
- INDICATIONS AND USAGE Dipyridamole tablets are indicated as an adjunct to coumarin anticoagulants in the prevention of postoperative thromboembolic complications of cardiac valve replacement.
Common Doses
- 100 mg
Dosage
DOSAGE AND ADMINISTRATION Adjunctive Use in Prophylaxis of Thromboembolism after Cardiac Valve Replacement The recommended dose is 75 to 100 mg four times daily as an adjunct to the usual warfarin therapy. Please note that aspirin is not to be administered concomitantly with coumarin anticoagulants.
Contraindications
- CONTRAINDICATIONS Hypersensitivity to dipyridamole and any of the other components.
Side Effects
- ADVERSE REACTIONS Adverse reactions at therapeutic doses are usually minimal and transient. On long-term use of dipyridamole tablets initial side effects usually disappear. The following reactions in Table 1 were reported in two heart valve replacement trials comparing dipyridamole tablets and warfarin therapy to either warfarin alone or warfarin and placebo: Table 1 Adverse Reactions Reported in 2 Heart Valve Replacement Trials Adverse Reaction Dipyridamole Tablets/ Placebo/ Warfarin Warfarin Number of patients 147 170 Dizziness 13.6% 8.2% Abdominal distress 6. 1% 3.5% Headache 2.3% 0.
Interactions
- Drug Interactions No pharmacokinetic drug-drug interaction studies were conducted with dipyridamole tablets. The following information was obtained from the literature. Adenosinergic agents (e.g., adenosine, regadenoson) Dipyridamole has been reported to increase the plasma levels and cardiovascular effects of adenosine. Adjustment of adenosine dosage may be necessary. Dipyridamole also increases the cardiovascular effects of regadenoson, an adenosine A 2A -receptor agonist.